The overall objective of this project is to describe and analyze a group of communities in the Connecticut Valley of Massachusetts, with consideration of both historic and contemporary patterns. The purpose of the project is both empirical and analytical. We intend to provide a descriptive demographic survey of the communities in question (located near the confluence of the Deerfield and Connecticut Rivers, Mass.) and to consider and develop theoretical implications raised. The emphasis is on those demographic factors that can be understood by analysis of fertility and migration data, but general trends of population growth, settlement, and distribution are an integral part of the research design. This area provides an excellent opportunity for pursuing this type of longitudinal demographic study because: a) the data are relatively complete and available for a long time period, and (b) it is a rare opportunity in which a colonizing population can be observed occupying a new environment, and analyzed from its very inception to its present-day manifestations. Our observations will ultimately be discussed in terms of their importance to studies in human microevolution, but almost equal emphasis is being placed on epidemiological and social-historical considerations. We consider the project to be relevant to several major issues in human population studies including: (a) secular trends in fertility and their relationship to other demographic and social factors. (b) the regional structure of human populations and methods for analysis. (c) the growth and spread of colonizing and rapidly growing human populations.